1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera including, light-shield means which is between an aperture opening of a camera body and a lens barrel, and is able to extend and contract in unison with movement of the lens barrel.
2. Related Art Statement
Heretofore, there have been proposed a variety of cameras each including, light-shield means which is between an aperture opening of a camera body and a lens barrel, and is able to extend and contract in unison with movement of the lens barrel.
For example, Japanese Utility Model Laid-Open No. 62-22639 discloses the structure of an extensible/contractible bellows for a camera which bellows is in a tapered tubular form having a rectangular section with its base end attached to a camera body and its tip end attached to a lens holder, and has four side surfaces each folded inward and outward alternately, wherein the bellows includes reinforcements made of an elastic linear material and disposed along outer ridges of the folded side surfaces. The disclosed bellows structure is employed in an instant camera so that camera can be folded up or set up when respectively put out of or into operation.
However, the bellows disclosed in Japanese Utility Model Laid-Open No. 62-22639 is intended to shield light by being extended or contracted when the camera is respectively folded up or set up, but it does not take into consideration zooming movement or the like. Accordingly, the disclosed bellows is not suitable for light-shielding of a lens barrel and an aperture of a lens shutter camera provided with zooming and focusing devices.
Also, Japanese Utility Model Laid-Open No. 58-115733 discloses a box-shaped bellows which has four ridges lying substantially in the extending direction in a position where the bellows is fully extended, wherein triangular folded portions are provided along the four ridges in alternate relation, and the folded portions locating in each surface defined pairs of the adjacent four ridges are arranged to be asymmetrical with respect to a central axis of the surface in the extending direction. The bellows thus constructed can be folded up into a smaller space.
In Japanese Utility Model Laid-Open No. 58-115733, however, no consideration is given as to how to prevent a flexion of the bellows.
Further, Japanese Patent Laid-Open No. 52-80025 discloses a camera of telescopic cylinder type that a light-shield cylinder for coupling a lens barrel and a camera body is provided in a portion of the camera rearwardly of the lens barrel, the light-shield cylinder comprising two light-shield cylinder members which are telescopically fitted to each other to be relatively movable in the direction of an optical axis, whereby the light-shield cylinder can be extended and contracted. The two light-shield cylinder members are dimensioned such that a cross-sectional area taken perpendicular to the optical axis, through which the flux of photographing light passes, is larger at the position closer to a film plane and is smaller at the position closer to a lens.
In the camera disclosed in Japanese Patent Laid-Open No. 52-80025, however, because the cross-sectional area of the light-shield cylinder is smaller in the position closer to the lens, an angle viewing from an image point on the film plane to the exit pupil, i.e., an angle h1 formed by the photographing light as indicated in FIG. 14, becomes also small. This raises the problem that a bright lens having a large aperture cannot be employed.
Moreover, Japanese Utility Model Publication No. 62-35083 discloses an intermediate ring (adapter) for close-range photographing which is attached to a lens mount surface of a single-lens reflex camera with a photographing lens attached to its front end. The disclosed intermediate ring has a manually operable cylinder disposed on the outermost peripheral side, and comprises a plurality of cylinders slidable in the direction of an optical axis, allowing the ring to be extended and contracted by manual operation. The plurality of slidable cylinders have respective engaging portions so that they are axially moved through mutual engagement.
However, because the structure disclosed in Japanese Utility Model Publication No. 62-35083 is not intended for being built in the camera, but for an adapter externally attached to the mount surface, most part of the ring is appeared outward. In particular, a large portion of outer circumstances of the cylinders is exposed to the outside for enabling manual operation, and steps between the plurality of cylinders fitted to each other in an extensible/contractible manner are visible from the outside, resulting in a complicated appearance.